1. Field of the Invention
The present invention may be generally classified in the field of oscillator circuitry, and more particularly, circuitry of this type specially adapted for use in simultaneous multi-frequency ultrasonic generators of the kind employed to resonate transducers associated with cleaning tanks in which articles are immersed in a liquid subjected to ultrasonic wave energy transmitted by the transducer or transducers.
2. Description of the Prior Art
It is already known to utilize the concept of resonating a transducer in a plurality of differing fundamental modes and their harmonics for transmitting, simultaneously, a multiplicity of frequencies in the ultrasonic range, through a liquid of a cleaning tank to which the transducer is attached. U.S. Pat. No. 3,371,233 issued to Edward G. Cook discloses this concept.
It has been found, however, that while this concept produces excellent results, and has found strong commercial acceptance, the oscillating circuitry embodied therein results in less output power than is truly desirable, in relation to the energy input to the oscillator. And, it is also considered that improved transistors, having higher reverse base-emitter breakdown voltage ratings, could be advantageously employed in the oscillation circuits, but for the fact that the present circuit configurations have a base drive network that is unsuitable for this purpose. Accordingly, while the existing circuitry as disclosed in the above mentioned patent is commercially acceptable, improvements therein are desirable for the purpose of making effective use of newly available transistor technology.